Quick question – should I update old post?

As from your experience should I update old post (from 2014)?

I have a site with about 100 posts, for the example, let say that the old post, 50 for our example does not have inner links and external links, tags, h2 etc, it was a lot of text without really organizing it…

Should I rewrite/update them or just leave them as they are now?

Another question, should I tweet old post that was not already tweet on twitter from the site ( as it was before I use twitter)?